Method for manufacturing a semiconductor structure and laser cutting device

Abstract

The embodiment of the present disclosure provides a preparation method of a semiconductor structure and a laser cutting device, wherein the preparation method comprises the following steps: providing a to-be-processed structure, the to-be-processed structure comprising cutting areas and functional areas located between adjacent cutting areas; generating an initial laser beam and performing a shaping operation on the initial laser beam to obtain a laser beam with a preset light spot; and guiding the laser beam to a middle region of the cutting area along a thickness direction. One of the laser beam and the to-be-processed structure is moved along a preset cutting track to adjust the relative position between the laser beam and the to-be-processed structure, and a modified layer and a crack extending from the modified layer along the thickness direction of the to-be-processed structure are formed in the to-be-processed structure by using the laser beam, wherein the preset light spot has a first symmetry axis perpendicular to the preset cutting track, and the energy distribution of the preset light spot on both sides of the first symmetry axis is asymmetrically distributed.

Description

Technical Field

[0001] This disclosure relates to the field of semiconductor technology, and in particular to a method for preparing a semiconductor structure and a laser cutting apparatus. Background Technology

[0002] In the semiconductor device manufacturing process, wafer dicing is a crucial step in separating the completed wafer into individual dies. Traditional wafer dicing technology primarily uses blade cutting. This method relies on a high-speed rotating blade to mechanically cut the wafer. However, due to the significant mechanical stress generated by blade cutting, edge chipping is easily caused, resulting in a loss of die yield. A more advanced dicing method is laser cutting, which effectively reduces edge chipping during wafer dicing, achieving high-quality dicing with near-zero edge damage.

[0003] However, the above process still presents the problem of reduced semiconductor device yield. Summary of the Invention

[0004] This disclosure provides a method for fabricating a semiconductor structure, including: Provide a structure to be processed, which includes a cutting area and a functional area located between adjacent cutting areas; An initial laser beam is generated and shaped to obtain a laser beam with a preset spot. The laser beam is then guided to the middle region of the cutting area along the thickness direction. The laser beam is moved along a preset cutting trajectory to adjust the relative position between the laser beam and the structure to be processed. The laser beam is used to form a modified layer and cracks extending from the modified layer along the thickness direction of the structure to be processed inside the structure to be processed. The preset light spot has a first axis of symmetry perpendicular to the preset cutting trajectory, and the energy distribution of the preset light spot on both sides of the first axis of symmetry is asymmetrical.

[0005] In some embodiments, along a first direction parallel to the direction of movement of the laser beam on the structure to be processed, the preset spot includes multiple regions with energy densities distributed from high to low.

[0006] In some embodiments, the number of regions is N, and the N regions are respectively denoted as the first region, the second region, ..., the Nth region, where N is a positive integer greater than or equal to 2. The second region, ..., the Nth region are sequentially placed around the outer periphery of the first region along a direction away from the geometric center of the first region. The geometric center of the Nth region coincides with the geometric center of the preset light spot, and the geometric centers of the first region, the second region, ..., the Nth region are offset in a second direction opposite to the first direction relative to the geometric center of the Nth region in a first direction.

[0007] In some embodiments, along a first direction, a preset light spot has a first end and a second end that are disposed opposite to each other, and the distance between the geometric center of the first region and the first end is less than the distance between the first region and the second end; Among them, the distance between the geometric center of the first region, the second region, ..., the Nth region and the first end increases sequentially.

[0008] In some embodiments, along a first direction, the distance between the geometric center points of adjacent regions is the same.

[0009] In some embodiments, forming a modified layer inside the structure to be treated by a laser beam includes: The energy from the first region to the Mth region in the preset light spot forms a modified layer inside the structure to be processed, where M is a positive integer and 1≤M<N.

[0010] In some embodiments, a structure to be processed is provided, the structure to be processed including a cutting area and a functional area located between adjacent cutting areas; including: A wafer is provided, which includes a substrate and a device layer on the substrate. A dicing region divides the substrate and device layer into multiple functional regions. Moving a laser beam along a preset cutting trajectory between the laser beam and the structure to be treated adjusts their relative positions, thereby forming a modified layer within the structure using the laser beam, including: The laser beam is moved along a preset cutting trajectory to adjust the relative position between the laser beam and the wafer. The laser beam irradiates the structure to be processed from the side of the substrate away from the device layer to form a modified layer inside the substrate and cracks extending from the modified layer along the thickness direction of the structure to be processed.

[0011] In some embodiments, a structure to be processed is provided, the structure to be processed including a cutting area and a functional area located between adjacent cutting areas; including: The system provides at least two wafers stacked vertically, with the exposed surfaces of the two outermost wafers defined as a first surface and a second surface, respectively, and a bonding layer disposed between adjacent wafers; a dicing region divides the stacked wafers into multiple functional areas. The laser beam is moved along a preset cutting trajectory to adjust the relative position between the laser beam and the structure to be treated. The laser beam is used to form a modified layer and cracks extending from the modified layer along the thickness direction of the structure to be treated within the structure, including: The laser beam is moved along a preset cutting trajectory to adjust the relative position between the laser beam and the at least two wafers. The laser beam irradiates the structure to be processed from the side where the first surface is located to form a first modified layer inside the bonding layer and a first crack extending from the first modified layer along the thickness direction of the structure to be processed. The laser beam is moved along a preset cutting trajectory to one of at least two wafers to adjust the relative position between the laser beam and the at least two wafers. The laser beam irradiates the structure to be processed from the side where the second surface is located to form a second modified layer inside the bonding layer and a second crack extending from the second modified layer along the thickness direction of the structure to be processed. The first modified layer and the second modified layer constitute the modified layer, and the first crack and the second crack constitute the crack.

[0012] In some embodiments, along a direction perpendicular to the cutting area, the cutting area includes an intermediate region providing a structure to be processed, including: A stress layer is formed on a predetermined surface in the thickness direction of the structure to be processed, extending into the interior of the structure to be processed, and the stress layer is located in the cutting area. In a direction parallel to the surface of the structure to be processed and perpendicular to the preset cutting trajectory, the preset light spot includes multiple preset regions with energy distributed from high to low. Guiding the laser beam to the middle region of the cutting area along the thickness direction includes: Align the preset area with the highest energy in the preset light spot with the edge of the stress layer away from the middle area, and align the preset area with the lowest energy in the preset light spot with the middle area.

[0013] In some embodiments, the energy value of the preset region with the lowest energy is 0.

[0014] In some embodiments, the laser beam includes a first laser beam and a second laser beam, the first laser beam having a preset spot, the maximum energy of the second laser beam being less than 1 / 20 of the maximum energy of the first laser beam, and the second laser beam being emitted within a preset time after the first laser beam is emitted.

[0015] In some embodiments, during the process of moving the laser beam along a preset cutting trajectory to one of the structures to be processed in order to adjust the relative position between the laser beam and the structure to be processed, the preset spots corresponding to the two laser beams emitted sequentially at any adjacent time are defined as the first preset spot and the second preset spot, respectively. The region with the lowest energy in the first preset spot is located at the edge of the first preset spot, and the lowest energy value in the first preset spot is denoted as A. Wherein, the orthographic projection of the first preset light spot on the structure to be processed and the orthographic projection of the second preset light spot on the structure to be processed have an overlapping area. Along the first direction parallel to the movement direction of the laser beam on the structure to be processed, the overlapping area is located in the middle region. The overlapping area is composed of the part where the orthographic projection of the region with energy value A in the first preset light spot on the structure to be processed overlaps with the orthographic projection of the region with energy value not less than A in the second preset light spot on the structure to be processed.

[0016] In some embodiments, after forming a modified layer inside the structure to be treated using a laser beam, the preparation method further includes: applying an external force to the structure to be treated, causing cracks to extend along the modified layer to the surface of the cutting area to divide the structure to be treated.

[0017] This disclosure also provides a laser cutting apparatus for cutting semiconductor structures, the apparatus comprising: A laser, used to generate an initial laser beam; The beam shaping unit is configured to perform shaping operations on the initial laser beam to obtain a laser beam with a preset spot. The focusing unit is used to guide the laser beam to the middle region along the thickness direction of the cutting area of ​​the structure to be treated, so as to form a modified layer and cracks extending from the modified layer along the thickness direction of the structure to be treated inside the structure to be treated. The motion unit moves one of the laser beam and the structure to be processed along a preset cutting trajectory to adjust the relative position between the laser beam and the structure to be processed. The preset light spot has a first axis of symmetry perpendicular to the preset cutting trajectory, and the energy distribution of the preset light spot on both sides of the first axis of symmetry is asymmetrical.

[0018] In some embodiments, the apparatus further includes an optical path unit configured to transmit an initial laser beam to a beam shaping unit.

[0019] In some embodiments, the beam shaping unit includes, but is not limited to, a laser beam adjuster or a structure consisting of multiple lenses.

[0020] In some embodiments, along a first direction parallel to the direction of movement of the laser beam on the structure to be processed, the preset spot includes multiple regions with energy densities distributed from high to low.

[0021] In some embodiments, the preset light spots corresponding to two laser beams emitted sequentially at any adjacent time are defined as the first preset light spot and the second preset light spot, respectively. The region with the lowest energy in the first preset light spot is located at the edge of the first preset light spot, and the lowest energy value in the first preset light spot is denoted as A. Wherein, the orthographic projection of the first preset light spot on the structure to be processed and the orthographic projection of the second preset light spot on the structure to be processed have an overlapping area. Along the first direction parallel to the movement direction of the laser beam on the structure to be processed, the overlapping area is located in the middle region. The overlapping area is composed of the part where the orthographic projection of the region with energy value A in the first preset light spot on the structure to be processed overlaps with the orthographic projection of the region with energy value not less than A in the second preset light spot on the structure to be processed.

[0022] The semiconductor structure fabrication method provided in this disclosure does not use a laser directly emitted from the laser-generating structure to cut the structure. Instead, it uses a laser beam obtained after a shaping process. The laser beam has a preset spot with an asymmetrical energy distribution on both sides of the first axis of symmetry. This effectively reduces the interference between two laser beams that irradiate the structure and are generated in adjacent time periods during the formation of the modified layer inside the structure. This significantly reduces structural damage and reduced electrical performance or reliability caused by interference between adjacent pulse laser points, thereby improving the yield, electrical performance, and reliability of the final semiconductor structure.

[0023] Details of one or more embodiments of this disclosure are set forth in the following drawings and description. Other features and advantages of this disclosure will become apparent from the specification and drawings. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 A flowchart illustrating a method for fabricating a semiconductor structure according to an embodiment of this disclosure; Figure 2 This is a schematic diagram of the structure to be processed provided in one embodiment of the present disclosure; Figure 3 A schematic diagram of a laser, an initial laser beam, a beam shaping unit, and a laser beam provided in an embodiment of this disclosure; Figure 4 One of the schematic diagrams of the preset light spot provided in different embodiments of this disclosure; Figure 5 A second schematic diagram of a preset light spot provided in different embodiments of this disclosure; Figure 6 A third schematic diagram of the preset light spot provided in different embodiments of this disclosure; Figure 7 Fourth of four schematic diagrams illustrating the preset light spots provided in different embodiments of this disclosure; Figure 8 for Figure 6 The energy distribution diagram of the preset light spot is shown; Figure 9 A schematic diagram illustrating the process of fabricating the semiconductor structure provided in this embodiment of the disclosure: wherein, Figure 9Figure (1) is a schematic diagram of the process of forming a modified layer by irradiating the interior of the structure to be treated with a laser beam. Figure 9 Figure (2) is Figure 9 The energy distribution curve of the preset spot corresponding to the laser beam in the first direction in Figure (1) is shown. Figure 10 A schematic diagram showing the arrangement of multiple preset light spots along a first direction in the cutting area during the fabrication process of the semiconductor structure provided in this embodiment of the disclosure; Figure 11 This is one of the schematic diagrams of the semiconductor structure during the fabrication process provided in the embodiments of this disclosure; Figure 12 This is the second schematic diagram of the semiconductor structure provided in the embodiments of this disclosure during the fabrication process; Figure 13 This is a schematic diagram of the structure to be processed provided in another embodiment of the present disclosure; Figure 14 This is a schematic diagram of the structure during the formation of the first modified layer and the second modified layer, provided in an embodiment of the present disclosure. Figure 15 This is a structural schematic diagram of the stress layer formation process provided in an embodiment of the present disclosure; Figure 16 This is a schematic diagram of the structure of the initial modified layer and the first laser beam provided in an embodiment of this disclosure; Figure 17 A schematic diagram of the structure of the modified layer and the second laser beam provided in the embodiments of this disclosure; Figure 18 This is a partial structural diagram of the test piece provided in the embodiments of this disclosure after the cutting process has been performed; Figure 19 This is a schematic diagram of the composition of a laser cutting apparatus provided in an embodiment of this disclosure. Detailed Implementation

[0026] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the specific embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0027] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of this disclosure. However, it will be apparent to those skilled in the art that this disclosure may be practiced without one or more of these details. In other instances, to avoid confusion with this disclosure, certain technical features well-known in the art have not been described; that is, not all features of actual embodiments are described herein, nor are well-known functions and structures described in detail.

[0028] In the accompanying drawings, for clarity, the dimensions of layers, areas, and elements, as well as their relative dimensions, may be exaggerated. The same reference numerals denote the same elements throughout.

[0029] It should be understood that when an element or layer is referred to as "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it may be directly on, adjacent to, connected to, or coupled to other elements or layers, or there may be intervening elements or layers. Conversely, when an element is referred to as "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc., may be used to describe various elements, components, areas, layers, and / or portions, these elements, components, areas, layers, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, area, layer, or portion from another element, component, area, layer, or portion. Therefore, without departing from the teachings of this disclosure, the first element, component, area, layer, or portion discussed below may be referred to as a second element, component, area, layer, or portion. And the discussion of a second element, component, area, layer, or portion does not imply that the first element, component, area, layer, or portion necessarily exists in this disclosure.

[0030] Spatial relation terms such as “below,” “under,” “below,” “below,” “above,” “above,” etc., are used herein for convenience of description to describe the relationship between one element or feature shown in the figure and other elements or features. It should be understood that, in addition to the orientation shown in the figure, spatial relation terms are intended to also include different orientations of the device in use and operation. For example, if the device in the figure is flipped, then the element or feature described as “below” or “below” other elements or features will be oriented “above” other elements or features. Therefore, the exemplary terms “below” and “under” can include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or otherwise) and the spatial descriptive terms used herein will be interpreted accordingly.

[0031] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. When used herein, the singular forms “a,” “an,” and “ / the” are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprise” and / or “comprising,” when used in this specification, identify the presence of features, integers, steps, operations, elements, and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts, and / or groups. When used herein, the term “and / or” includes any and all combinations of the associated listed items.

[0032] In semiconductor manufacturing, after integrated circuits are formed on a wafer, the wafer needs to be diced into several individual dies. These dies are then individually packaged or laminated and bonded together to form individual chips. With the continuous improvement of device integration and dicing technology, stealth dicing (SD) has gradually become mainstream. However, during the stealth dicing process, there are still issues such as significant yield losses or poor performance in the final structure, such as poor electrical performance.

[0033] Based on this, the following technical solutions for embodiments of this disclosure are proposed: This disclosure provides a method for fabricating a semiconductor structure, such as... Figure 1 The preparation method includes the following steps: Step S101: Provide a structure to be processed, which includes a cutting area and a functional area located between adjacent cutting areas; Step S102: Generate an initial laser beam, and perform a shaping operation on the initial laser beam to obtain a laser beam with a preset spot, and guide the laser beam to the middle region of the cutting area along the thickness direction; Step S103: Move the laser beam and one of the structures to be processed along the preset cutting trajectory to adjust the relative position between the laser beam and the structure to be processed, and use the laser beam to form a modified layer and cracks extending from the modified layer along the thickness direction of the structure to be processed inside the structure to be processed. The preset light spot has a first axis of symmetry perpendicular to the preset cutting trajectory, and the energy distribution of the light spot on both sides of the first axis of symmetry is asymmetrical.

[0034] The semiconductor structure fabrication method provided in this disclosure does not use a laser directly emitted from the laser-generating structure to cut the structure. Instead, it uses a laser beam obtained after a shaping process. The laser beam has a preset spot with an asymmetrical energy distribution on both sides of the first axis of symmetry. This effectively reduces the interference between two laser beams that irradiate the structure and are generated in adjacent time periods during the formation of the modified layer inside the structure. This significantly reduces structural damage and reduced electrical performance or reliability caused by interference between adjacent pulse laser points, thereby improving the yield, electrical performance, and reliability of the final semiconductor structure.

[0035] To make the above-mentioned objects, features, and advantages of this disclosure more apparent and understandable, the specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. In describing the embodiments of this disclosure in detail, for ease of explanation, the schematic diagrams may be partially enlarged without adhering to general proportions, and the schematic diagrams are merely examples and should not limit the scope of protection of this disclosure.

[0036] Figure 2 This is a schematic diagram of the structure to be processed provided in one embodiment of the present disclosure; Figure 3 A schematic diagram of a laser, an initial laser beam, a beam shaping unit, and a laser beam provided in an embodiment of this disclosure; Figure 4 One of the schematic diagrams of the preset light spot provided in different embodiments of this disclosure; Figure 5 A second schematic diagram of a preset light spot provided in different embodiments of this disclosure; Figure 6 A third schematic diagram of the preset light spot provided in different embodiments of this disclosure; Figure 7 Fourth of four schematic diagrams illustrating the preset light spots provided in different embodiments of this disclosure; Figure 8 for Figure 6 The energy distribution diagram of the preset light spot is shown; Figure 9 A schematic diagram illustrating the process of fabricating the semiconductor structure provided in this embodiment of the disclosure: wherein, Figure 9 Figure (1) is a schematic diagram of the process of forming a modified layer by irradiating the interior of the structure to be treated with a laser beam. Figure 9 Figure (2) is Figure 9 The energy distribution curve of the preset spot corresponding to the laser beam in the first direction in Figure (1) is shown. Figure 10 A schematic diagram showing the arrangement of multiple preset light spots along a first direction in the cutting area during the fabrication process of the semiconductor structure provided in this embodiment of the disclosure; Figure 11 This is one of the schematic diagrams of the semiconductor structure during the fabrication process provided in the embodiments of this disclosure; Figure 12 This is the second schematic diagram of the semiconductor structure provided in the embodiments of this disclosure during the fabrication process; Figure 13This is a schematic diagram of the structure to be processed provided in another embodiment of the present disclosure; Figure 14 This is a schematic diagram of the structure during the formation of the first modified layer and the second modified layer, provided in an embodiment of the present disclosure. Figure 15 This is a structural schematic diagram of the stress layer formation process provided in an embodiment of the present disclosure; Figure 16 This is a schematic diagram of the structure of the initial modified layer and the first laser beam provided in an embodiment of this disclosure; Figure 17 A schematic diagram of the structure of the modified layer and the second laser beam provided in the embodiments of this disclosure; Figure 18 This is a partial structural diagram of the structure to be processed after the cutting process is performed, as provided in the embodiments of this disclosure.

[0037] The preparation method provided in the embodiments of this disclosure will be further described in detail below with reference to the accompanying drawings.

[0038] The technical solutions provided in this disclosure relate to the field of chip fabrication (DP) in semiconductor packaging technology, and are applicable to the process of obtaining independent chip structures by using stealth dicing to process the structure SS to be processed.

[0039] First, execute step S101, as follows: Figure 2 and Figure 13 As shown, a structure SS to be processed is provided, which includes a cutting area Qb and a functional area Qa located between adjacent cutting areas Qb.

[0040] Here, the structure to be processed SS can be a single wafer structure, a structure formed by stacking multiple wafer structures in the vertical direction, or a die structure containing one or more chip structures. The wafer or die is provided with multiple chip structures and multiple dicing regions Qb located between the multiple chip structures. When the multiple chip structures (or multiple stacked chip structures, applicable to the case where the structure to be processed SS is a structure of multiple stacked wafers W) are separated in the subsequent separation operation, the position where the dicing region Qb is located can be broken to achieve separation between the multiple chip structures.

[0041] In some embodiments, such as Figure 2 As shown, a structure SS to be processed is provided, which includes a cutting region Qb and a functional region Qa located between adjacent cutting regions Qb; including: A wafer W is provided, which includes a substrate 10 and a device layer L2 located on the substrate 10. A dicing region Qb divides the substrate 10 and the device layer L2 into multiple functional regions Qa.

[0042] Here, substrate 10 can be a semiconductor substrate; the material of the semiconductor substrate specifically includes elemental semiconductor materials (e.g., silicon (Si) substrates, germanium (Ge) substrates, etc.), or III-V compound semiconductor materials (e.g., gallium nitride (GaN) substrates, gallium arsenide (GaAs) substrates, indium phosphide (InP) substrates, etc.), or II-VI compound semiconductor materials, or organic semiconductor materials, or other semiconductor materials known in the art. In a specific embodiment, the substrate can be a silicon substrate.

[0043] In other embodiments, such as Figure 13 As shown, a structure SS to be processed is provided, which includes a cutting region Qb and a functional region Qa located between adjacent cutting regions Qb; including: At least two wafers W are provided and stacked in a vertical direction. The exposed surfaces of the two outermost wafers W are defined as the first surface S1 and the second surface S2, respectively. A bonding layer L1 is provided between adjacent wafers W. A dicing region Qb divides the stacked wafers W into multiple functional regions Qa.

[0044] In some embodiments, such as Figure 13 As shown, taking two wafers W stacked vertically as an example, the structure to be processed SS may include a first wafer W1 and a second wafer W2 stacked along the thickness direction of the structure to be processed SS. The first wafer W1 includes a second substrate 31 and a first bonding layer L11. The second wafer W2 includes a third substrate 32 and a second bonding layer L12. The first bonding layer and the second bonding layer L12 are bonded to each other to form a bonding layer L1. The first surface S1 is located on the first wafer W1, and the second surface S2 is located on the second wafer W2.

[0045] In some embodiments, the wafer or chip structure included in the structure to be processed SS may include, but is not limited to, logic wafers (or chips), such as, but not limited to, graphics processing units (GPUs), field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), central processing units (CPUs), or other known electronic circuits used as processors. Alternatively, the structure to be processed SS may also be a dynamic random access memory (DRAM) memory or other types of memory structures.

[0046] In some embodiments, the structure to be processed SS may also be a product such as fifth-generation double-rate synchronous dynamic random access memory (DDR5), fifth-generation low-power double-rate synchronous dynamic random access memory (LPDD5X), or high-bandwidth memory (HBM) in high-end storage.

[0047] It should be noted that the types of structures SS to be processed listed in the embodiments of this disclosure are only a part of the structures applicable to stealth dicing technology. The solutions provided in the embodiments of this disclosure can also be applied to other types and structures of semiconductor devices.

[0048] Next, proceed to step S102, as follows: Figures 3 to 12 as well as Figure 13 and Figure 14 As shown, Figure 11 and Figure 12 For along Figure 2 Detailed sectional view taken along the B1-B2 direction. Figure 14 For along Figure 13 A detailed cross-sectional view taken along the C1-C2 direction is used to generate an initial laser beam 20a. The initial laser beam 20a is then shaped to obtain a laser beam 20 with a preset spot 21. The laser beam 20 is then guided to the middle region of the cutting area Qb along the thickness direction. Step S103 is then executed, moving one of the laser beam 20 and the structure to be processed SS along the preset cutting trajectory D0 to adjust the relative position between the laser beam 20 and the structure to be processed SS. The laser beam 20 is used to form a modified layer 11 inside the structure to be processed SS, and a crack 12 extending from the modified layer 11 along the thickness direction of the structure to be processed SS. The preset light spot 21 has a first axis of symmetry Oa perpendicular to the preset cutting trajectory D0, and the energy distribution of the preset light spot 21 on both sides of the first axis of symmetry Oa is asymmetrical.

[0049] Here, the process of generating a modified layer 11 and cracks 12 extending from the modified layer 11 along the thickness direction of the structure SS in the structure to be treated by a laser beam can be understood as a stealth cutting process. In this process, stealth cutting is achieved by focusing high-frequency pulsed laser energy onto a focal point inside the silicon layer through the material on one side of the structure SS (e.g., including but not limited to the back silicon layer). The high energy density at the pulse focal point forms a silicon (Si) modified region, and then the microcracks formed by thermal shock extend to the surface, causing multiple chips to separate from each other.

[0050] In some embodiments, the initial laser beam 20a may be generated by a laser A1, which may include, but is not limited to, any laser that emits a laser beam to form a modified layer inside the structure SS to be treated.

[0051] In some embodiments, laser A1 is at least one of lasers that emits near-infrared laser, far-infrared laser, or other infrared bands, green laser, or ultraviolet laser, and the emitted laser pulse width is nanosecond, picosecond, or femtosecond.

[0052] In some embodiments, laser A1 is at least one of lasers capable of emitting near-infrared or far-infrared wavelengths.

[0053] In some embodiments, the initial laser beam 20a emitted by laser A1 is a Gaussian beam, with its energy distributed in a "bell-shaped" pattern across its cross-section, high in the center and gradually decreasing towards the edges. This can also be understood as the energy distribution being strongest at the beam center and weakest towards the edges. In a Gaussian beam, the spot exhibits a circularly symmetrical energy distribution. Figure 3 In the attached diagram, which points to the upper right corner corresponding to the dashed arrow of the initial laser beam 20a, it can be seen that the energy of the initial laser beam 20a spot is symmetrically distributed about the axis of symmetry O0 of the pattern formed by the edge of the spot.

[0054] In conventional techniques, to mitigate splash damage during stealth dicing, adjustments to recipe parameters (or parameter optimization methods) are typically employed to minimize it. However, as some advanced process wafers become increasingly sensitive to laser-induced splash damage, conventional parameter adjustments are no longer sufficient to effectively reduce this damage. This makes reducing splash damage to a safe level increasingly challenging. For instance, in demanding chip structures, reducing the splash damage distance to below 10µm has become a difficult problem.

[0055] During stealth dicing, at the focal point of the pulsed laser, adjacent pulse points have a small spacing of micrometers (µm) and concentrated energy density. Interference in the heat-affected zone between adjacent laser points easily leads to random laser diffraction, causing splash damage. If this damage penetrates the active area of ​​the chip, it results in yield loss. Laser splash damage directly affects chip yield and can even cause some energy to exceed the dicing range and penetrate the active area of ​​the chip, damaging the crystal and metal layers. Furthermore, because splash damage is small and located in an internal region, it is difficult for subsequent measurement processes to detect effectively.

[0056] In this disclosed embodiment, based on the spatial characteristics of laser pulse spots and research on pulsed laser cutting technology (stealth cutting), the applicant of this application proposed a method to reduce splash damage by changing the beam power distribution of a Gaussian beam. The main idea is to change the power (energy) distribution of the Gaussian beam pulse spot from a symmetrical distribution to an asymmetrical distribution, thereby achieving spatial filtering and reducing or eliminating splash damage caused by interference between adjacent pulse laser points. This method can also be called beam skewness spatial filtering adjustment.

[0057] In some embodiments, wavefront phase modulation of the light spot can be achieved by performing a shaping operation on the initial laser beam 20a, thereby changing the energy distribution pattern in the light spot. Figure 3 In the attached diagram at the upper right corner, corresponding to the dashed arrow pointing to laser beam 20, it can be seen that the energy of the laser beam 20 spot has a relationship with respect to the preset spot 21 (see subsequent appendices for details). Figure 4 To be continued Figure 7 The first axis of symmetry Oa of the pattern formed by the edges is distributed asymmetrically. This helps to reduce or eliminate splash damage caused by interference between adjacent laser points during the cutting process of the structure SS to be processed.

[0058] This situation can be further explained as follows: If an initial laser beam 20a without shaping is used to directly cut the structure to be processed, after the first pulse forms a modification at point A on the material inside the structure, the next pulse will immediately form a modification at point B next to point A. At this time, if the residual heat at point A has not dissipated, or if the shock wave / splash generated at point A can easily affect or cause problems at point B, or if heat, shock wave / splashes may travel outside the intended cutting area, causing damage to the normal structure or short circuits, which can easily reduce the electrical performance and reliability of the final semiconductor structure. However, when a laser beam 20 that has undergone shaping is used, because the energy distribution of its preset spot 21 on both sides of the first axis of symmetry Oa is asymmetrical, for example, when using... Figure 3The energy change of the preset laser spot 21 is set to be strong at first and then weak. This helps to reduce the amount of residual heat generated by the previous laser pulse during the formation of point B, and also reduces the probability of shock waves / splashes traveling to other locations. It confines the heat and shock waves / splashes to the area within the structure SS to be processed, significantly reducing or preventing their migration to other areas, such as towards functional region Qa. It can be seen that the laser beam after shaping reduces interference between adjacent laser pulses, significantly reducing sputtering damage, improving the electrical performance and reliability of the final semiconductor structure, and increasing production yield.

[0059] In some embodiments, such as Figures 4 to 7 As shown, along a first direction parallel to the direction of movement of the laser beam 20 on the structure SS to be processed, the preset spot 21 includes multiple regions Q with energy densities distributed from high to low.

[0060] Here, the first direction is the direction parallel to the surface of the structure to be processed SS. The first direction is consistent with the direction of movement of the laser beam 20 on the structure to be processed SS. It can also be understood that in the process of stealth cutting, if the laser beam 20 is moved to perform the cutting operation, then the direction of movement of the laser beam 20 is the first direction. However, if the structure to be processed SS is used to perform the cutting operation, then the direction opposite to the direction of movement of the structure to be processed SS is the first direction.

[0061] In some embodiments, such as Figure 4 As shown, along a first direction parallel to the movement direction of the laser beam 20 on the structure SS to be processed, the preset spot 21 includes multiple regions Q with energy densities distributed from high to low. The boundary shape of the preset spot 21 is elliptical. The multiple regions Q are divided into multiple transverse partitions along the major axis of the ellipse by multiple convex arc-shaped boundary lines, which correspond to the first region Q1, the second region Q2, ..., the (N-1)th region Q(n-1), and the Nth region Qn, respectively. Adjacent partitions (regions Q) are separated from each other by a common arc-shaped boundary Lb (i.e., a common boundary line).

[0062] In some embodiments, the arc-shaped boundary Lb protrudes in the direction from the first region Q1 to the second region Q2. This arrangement is beneficial for increasing the size of the region Q with higher energy in the preset laser spot. Thus, when the initial laser beam 20a is shaped to obtain a laser beam 20 with a non-uniform energy distribution, the aforementioned improvement effect can be achieved without affecting the generation of the modified layer 11 and the cracks 12 extending from the modified layer 11. This is beneficial for achieving the aforementioned improvement effect without affecting the smooth implementation of the cutting process.

[0063] Continue to refer to Figure 4The ellipse formed by the boundary of the preset light spot 21 has a second axis of symmetry Ob (the extension direction is consistent with the extension direction of the major axis of the ellipse), and the energy distribution on both sides of the second axis of symmetry Ob is symmetrical. In this way, the modified layer 11 and the cracks extending from the modified layer 11 can be regularly distributed in the cutting region Qb, preventing breakage or damage at unwanted locations during the process of dividing multiple chip structures due to scattered distribution. This is beneficial to improving the cutting yield and the integrity, electrical performance and reliability of the final semiconductor structure.

[0064] In some embodiments, such as Figure 5 As shown, along a first direction parallel to the movement direction of the laser beam 20 on the structure SS to be processed, the preset spot 21 includes multiple regions Q with energy densities distributed from high to low. The boundary shape of the preset spot 21 is elliptical. The multiple regions Q are divided into multiple partitions along the major axis of the ellipse, corresponding to the first region Q1, the second region Q2, ..., the (N-1)th region Q(n-1), and the Nth region Qn, respectively. Adjacent partitions (regions Q) are separated from each other by a common boundary line Lc. The multiple boundary lines Lc protrude in the direction from the first region to the second region and have a common intersection point A05 at the end of the first region Q1 away from the second region Q2.

[0065] Compared to the previous embodiment, this embodiment achieves precise control over the energy distribution within the light spot. Lower-energy regions surround higher-energy regions over a larger area, increasing the transition range from high to low energy. This facilitates the formation of a more regular and controllable modified layer, leading to smoother formation of the modified layer and the cracks 12 extending along it. It can be seen that this embodiment, in addition to achieving the effects of the previous embodiment, further contributes to the smooth execution of the cutting process.

[0066] In some embodiments, such as Figure 6 as well as Figure 8 As shown, there are N regions Q. These N regions Q are denoted as region Q1, region Q2, region Q3, ..., region Qn, where N is a positive integer greater than or equal to 2. Regions Q2, ..., region Qn are defined along the geometric center of region Q1 (corresponding to the attached diagram). Figure 6 The direction of point O1 in the first region Q1 is sequentially overlaid on the outer perimeter of the first region Q1, and the geometric center of the Nth region Qn (corresponding to the attached) is... Figure 6 Point On in the image) and the geometric center of the preset light spot 21 (corresponding to the attached image) Figure 6 The points O in the region coincide, and the geometric centers of the first region Q1, the second region Q2, ..., the Nth region Qn (corresponding to the points O in the appendix) are respectively attached. Figure 6 Points O1, O2, ..., and On in the first direction are relative to the geometric center of the Nth region Qn (corresponding to the attached diagram). Figure 6 Point O in the middle is offset in a second direction opposite to the first direction.

[0067] Continue to refer to Figure 6 Along the first direction, the preset light spot 21 has a first end A01 and a second end A02 that are relatively set, and the geometric center of the first region Q1 (corresponding to the attached) Figure 6 The distance between point O1 and the first end A01 is less than the distance between point O1 and the second end A02; Among them, the geometric centers of the first region Q1, the second region Q2, ..., the Nth region Qn (corresponding to the attached...) Figure 6 The distances between points O1, O2, ..., and On and the first end A01 increase sequentially.

[0068] In this embodiment, when the overall energy distribution still maintains a high-to-low distribution trend along the first direction and the regions with higher energy are generally located near the first end A01, the energy of N regions exists along the geometric center of the first region Q1 (corresponding to the attached...). Figure 6 The energy distribution from high to low along a large distance in the first direction from point O1 to the second end A02, and the arrangement along the geometric center of the first region Q1 (corresponding to the attached) Figure 6 Point O1 in the diagram points to a second direction from the first end A01, forming a region with energy distribution from high to low over a short distance. Simultaneously, there is also an energy distribution from high to low in directions intersecting with either the first or second direction. This arrangement facilitates achieving a highly uniform energy distribution trend across multiple regions while minimizing sputtering damage, thus promoting the formation of a continuous, uniform, and consistent-width modified layer. In comparison, this design offers multiple advantages, including effectively suppressing crack branching, achieving directional propagation, reducing the heat-affected zone, and improving cutting quality. Meanwhile, in this embodiment, the preset spot 21 is adjusted along the cutting direction to have an energy spatial distribution that is strong first and then weak. This means that even if the distance between adjacent pulse points and the geometric center of the pulse points does not change, the energy distribution changes, making the weak energy region of the previous pulse point adjacent to the energy region of the next pulse point. This significantly reduces the derivative impact on the next pulse. This is because the presence of the weak energy region in the previous pulse point causes the material modification (e.g., silicon modification) area of ​​the structure to be processed to be smaller or not yet modified. When the next laser pulse point acts on the interior of the structure to be processed (SS), sputtering is less likely to occur, which helps to improve the cutting yield and reduce the occurrence of device damage or poor electrical performance.

[0069] In some embodiments, along the first direction, the geometric center point between adjacent regions Q (corresponding to the attached) Figure 6The distances between points O1, O2, ..., and any two adjacent points in point On are all the same. This helps to obtain a laser beam with controllable energy distribution, thereby obtaining a controllable modified layer and cracks with controllable propagation direction.

[0070] In some embodiments, the laser beam 20 forms a modified layer 11 inside the structure SS to be treated, including: The energy from the first region Q1 to the Mth region in the preset light spot 21 forms a modified layer 11 inside the structure to be processed SS, where M is a positive integer and 1≤M<N.

[0071] In any of the above embodiments, the value of N can be one of 2, 3, 4, and 5, but is not limited thereto. It can also be one of the positive integers greater than 5 and less than or equal to 10, or it can be a positive integer greater than 10. There is no specific limitation here, and it can be set as needed.

[0072] Understandably, when the number of regions Q is large (e.g., greater than 5), it helps to achieve a smooth transition in energy distribution, obtain a laser beam with highly controllable energy distribution, and achieve precise control of the stealth cutting process. Conversely, when the number of regions Q is small (e.g., greater than or equal to 2 and less than or equal to 5), it helps to reduce the difficulty of the shaping operation, distinguishing which regions are in the energy range greater than or equal to the ablation threshold (where modification is possible) and which regions are in the energy range less than the ablation threshold (where modification is not achieved or the desired modification cannot be achieved). This facilitates accurate shaping operations based on factors such as the material configuration of the regions requiring material modification in the structure to be processed, the size of the modification area in a single pulse, the spacing between the regions affected by adjacent pulse points, or the overlap between the orthographic projections of adjacent laser beams on the structure to be processed, thus obtaining the desired laser beam.

[0073] In some embodiments, such as Figure 7 As shown, in a third direction D3 that is parallel to the surface of the structure to be processed SS and perpendicular to the preset cutting trajectory D0, the preset light spot 21 includes multiple preset regions Qc with energy distributed from high to low. Along the first direction, the preset light spot 21 includes a third end A03 and a fourth end A04 located at the edge. The energy of the preset light spot 21 located on both sides of the first axis of symmetry Oa is asymmetrically distributed.

[0074] In some embodiments, such as Figure 7 As shown, the energy of any preset region Qc near the third end A03 is greater than the energy of the portion near the fourth end A04, and on the third direction D3, the energy of the portions located in different preset regions Qc near the fourth end A04 decreases sequentially.

[0075] In some embodiments, the energy difference between the adjacent third end A03 portion and the adjacent fourth end A04 portion located in the same preset region Qc is no greater than 10% of the highest energy value in the preset region Qc, so as to help ensure the cutting effect.

[0076] In this embodiment, the laser beam 20 corresponding to the preset spot 21 can be targeted at subsequent attachments. Figure 15 The provided structure enables the cutting operation; the specific operation and effects will be explained in a later section.

[0077] In some embodiments, such as Figure 9 (1) Figure in Figure 9 Figure (2) in the middle and Figures 10 to 12 As shown, the laser beam 20 and the structure SS to be processed are moved along a preset cutting trajectory D0 to adjust the relative position between the laser beam 20 and the structure SS. The laser beam 20 is used to form a modified layer 11 inside the structure SS, including: The laser beam 20 and the structure to be processed SS are moved along the preset cutting trajectory D0 to adjust the relative position between the laser beam 20 and the wafer W. The laser beam 20 irradiates the structure to be processed SS from the side of the substrate 10 away from the device layer L2 to form a modified layer 11 and a crack 12 extending from the modified layer 11 along the thickness direction of the structure to be processed SS inside the substrate 10.

[0078] In the appendix Figure 9 In this process, one of the laser beam 20 and the structure SS to be processed is moved along the preset cutting trajectory D0 to adjust the relative position between the laser beam 20 and the wafer W. The change in their relative position is achieved by moving the position of the laser beam 20. In this case, the first direction is the same as the direction of the preset cutting trajectory D0. However, this is not the only possibility. In other embodiments, the change in their relative position can also be achieved by moving the structure SS to be processed. In this case, the first direction is opposite to the direction of the preset cutting trajectory D0.

[0079] In this process, the laser beam 20 passes through the focusing unit A3 and then irradiates the surface of the structure to be treated SS before continuing to advance and eventually reaching the interior of the substrate 10 to form the modified layer 11.

[0080] In some embodiments, the focusing unit A3 is a lens 30.

[0081] In the appendix Figure 9 (1) Figure in Figure 9 Figure (2) and appendix Figure 10 The image shows a preset spot 21 of laser beam 20. Figure 6 The embodiment performs the cutting operation in the attached Figure 9In Figure (1), besides showing the formation of a modified layer 11 inside the structure SS by the cutting operation and the crack 12 extending along the thickness direction of the structure SS from the location of the modified layer 11, the energy distribution of the preset spot 21 of the laser beam 20 inside the structure SS is also clearly shown in Figure (1). Figure 9 In Figure (1), below the structure to be processed SS, a schematic diagram is shown regarding the energy distribution of the preset light spot 21 on the cutting area Qb. In this figure, the direction of the pre-cutting trajectory D0 is the same as the first direction. In the first direction, the energy in the preset light spot is distributed in a way that is strong at first and then weak. Figure 9 In Figure (2), curve La is the energy distribution curve at the position of line E1-E2 containing the second axis of symmetry Ob. The trend of energy distribution can also be seen. The triangular area shown by the dashed line is the spatial transmission area of ​​laser beam 20.

[0082] In addition, in the appendix Figure 10 The diagram also shows the arrangement of the preset spot 21 contained in the laser beam involved in the cutting operation on the structure SS to be processed, which will be explained below with reference to the accompanying drawings: In some embodiments, such as Figure 10 As shown, the correspondence between the preset light spot 21 and the horizontal coordinate X is as follows: Figure 9 In the figure (1), the relationship between the second axis of symmetry Ob and the preset spot 21 corresponds to the process of moving the laser beam 20 along the preset cutting trajectory D0 and one of the structures to be processed SS to adjust the relative position between the laser beam 20 and the structure to be processed SS. During this process, the preset spots 21 corresponding to the two laser beams 20 emitted in any adjacent time are defined as the first preset spot 211 and the second preset spot 212, respectively. The region with the lowest energy in the first preset spot 211, that is, the Nth region Qn, is located at the edge of the first preset spot 211, and the lowest energy value in the first preset spot 211 is recorded as A. Wherein, the orthographic projection of the first preset spot 211 on the structure to be processed SS and the orthographic projection of the second preset spot 212 on the structure to be processed SS have an overlapping region Qd. Along a first direction parallel to the movement direction of the laser beam 20 on the structure to be processed SS, the overlapping region Qd is located in the middle region of the structure composed of the first preset spot 211 and the second preset spot 212. The overlapping region Qd is the region in the first preset spot 211 with an energy value of A, that is, the part that overlaps with the orthographic projection of the Nth region Qn on the structure to be processed SS and the orthographic projection of the region in the second preset spot 212 with an energy value not less than A on the structure to be processed SS.

[0083] It should be noted that, although in Figure 10The diagram illustrates the overlap in the overlapping region Qd, where the Nth region of the first preset spot 211 with the lowest laser energy density overlaps with the second preset spot 212 with the lowest energy density region Qn, the (N-1)th region Q(n-1) with a slightly higher energy density than the Nth region, and the (N-2)th region Q(n-2) with a slightly higher energy density than the (N-1)th region Q(n-1). This is merely an illustrative example and does not constitute a limitation. Similarly, in the appendix... Figure 10 The area with energy density higher than the ablation threshold, corresponding to the content above the dashed line Ld, is also an illustrative example and is not intended to limit which region's energy level can produce a quality improvement effect in the embodiments of this disclosure.

[0084] In some embodiments, the number of regions in N regions Q that can produce an ablation effect is not less than 1 and less than N, or it can be greater than 1 and less than or equal to N. However, it should be noted that in this case, the energy level in the Nth region can be set to be equal to the ablation threshold in order to reduce sputtering damage caused by interference between adjacent pulse points.

[0085] In some embodiments, the Nth region with the lowest energy density in the first preset spot 211 may have an overlap region Qd with at least one of the other regions Q besides the first region Q1. In actual operation, this can be set as needed and is not specifically limited here.

[0086] Understandably, while maintaining the aforementioned settings, regardless of the overlapping region Qd in the adjacent preset spot 21, the overlapping region is set to reduce sputtering damage compared to the case where there is a region with the highest energy in the overlapping region, so that the semiconductor structure can ultimately achieve the aforementioned excellent effect.

[0087] In some embodiments, the energy of the preset spot 21 located in the overlap region Qd is lower than the ablation threshold, which can be understood as the minimum laser energy density required to modify the target layer in the structure SS to be processed. In this case, the weak-energy region of the previous pulse cannot form a significant polycrystalline silicon modification region, thus cutting off the physical basis for sputtering in the subsequent pulse. Figure 18 The test piece SSa shown is an effect diagram of the modified region 11c obtained by using the laser beam 20 provided in the embodiment of this disclosure in the cutting region Qba. It can be seen that not only did no sputtering damage occur in the functional region Qaa, but the scattering distance of sputtering damage in the cutting region Qbb was significantly reduced from ≤ 20um (corresponding to the width direction dimension of the cutting region Qba) before improvement to ≤ 8um (corresponding to the width direction dimension of the cutting region Qba) after improvement, which meets the requirements of advanced process technology.

[0088] In some embodiments, the test piece SSa can be a dedicated tin-plated (Sn) sheet for splash damage measurement. Since the melting point of the tin-plated (Sn) sheet is lower (232°) than that of Si (1414°), it is more sensitive to heat and can better reflect the condition of the test damage.

[0089] In some embodiments, the modified layer 11 may include a first modified region 112 and a second modified region 111. The first modified region 112 is the region where modification occurs, and the second modified region 111 may correspond to the modified region generated by the laser energy in the overlapping region Qd of adjacent pulse points. This can be a case of partial modification, particularly where the location adjacent to the next laser pulse point (which can be understood as a small region where the laser beam produces a modification effect after focusing inside the material) is unmodified. This is beneficial for further reducing sputtering damage caused by interference between adjacent pulse points due to the heat-affected zone.

[0090] In other embodiments, such as Figure 13 and Figure 14 As shown, the laser beam 20 and the structure SS to be processed are moved along a preset cutting trajectory D0 to adjust their relative positions. The laser beam 20 is used to form a modified layer 11 and a crack 12 extending from the modified layer 11 along the thickness direction of the structure SS inside the structure SS, including: The laser beam 20 is moved along the preset cutting trajectory D0 to adjust the relative position between the laser beam 20 and the at least two wafers W. The laser beam 20 irradiates the structure to be processed SS from the side where the first surface S1 is located, that is, the side of the first wafer W1 away from the bonding layer L1, so as to form a first modified layer L11a inside the bonding layer L1 and a first crack 121 extending from the first modified layer L11a along the thickness direction of the structure to be processed SS. The laser beam 20 is moved along the preset cutting trajectory D0 to adjust the relative position between the laser beam 20 and the at least two wafers W. The laser beam 20 irradiates the structure to be processed SS from the second surface S2, that is, the side where the second wafer W2 is located, to form a second modified layer L12a and a second crack 122 extending from the second modified layer L12a along the thickness direction of the structure to be processed SS inside the bonding layer L1. The first modified layer L11a and the second modified layer L12a constitute the modified layer 11, and the first crack 121 and the second crack 122 constitute the crack 12.

[0091] In any of the above embodiments, after the cutting operation is completed, in addition to the formation of crack 12 in the thickness direction of the structure to be processed SS, the modified layer 11 will also have cracks in the direction extending along the cutting area Q, so that the separation operation of the structure to be processed SS can be successfully achieved.

[0092] In some other embodiments, such as Figure 2 , Figure 7 as well as Figure 15 As shown, along the direction perpendicular to the cutting region Qb (the direction of the cutting region width), the cutting region Qb includes a middle region Qb1, providing the structure SS to be processed, including: by Figure 2 Taking the structure to be processed SS as an example, a stress layer L3 is formed on the preset surface S3 of the structure to be processed SS in the thickness direction D2, extending into the interior of the structure to be processed SS. The stress layer L3 is located in the cutting area Qb. like Figure 7 As shown, in a third direction D3 that is parallel to the surface of the structure to be processed SS and perpendicular to the preset cutting trajectory D0, the preset spot 21 includes multiple preset regions Qc with energy distributed from high to low. The laser beam 20 is guided to the middle region of the cutting area Qb along the thickness direction D2, including: Align the preset region Qc with the highest energy in the preset spot 21 with the edge of the stress layer L3 away from the middle region Qb1, that is, with the edge of the surrounding region Qb2 on both sides of the middle region in the width direction of the cutting region Qb away from the middle region Qb1, and align the preset region Qc with the position of the middle region Qb1.

[0093] In some embodiments, forming a stress layer L3 includes: Before laser cutting, the cutting area Qb is pretreated to alter its physical properties, making it less sensitive to subsequent laser energy. Specifically, low-energy, large-spot ultraviolet lasers or plasma can be used to perform non-destructive surface treatment on the location corresponding to the cutting area Qb on the back of the silicon wafer, forming an extremely thin (nanoscale) compressive stress layer. This stress layer alters the local refractive index and absorption coefficient of the material.

[0094] During the cutting operation after the formation of stress layer L3, such as Figure 7 As shown, the preset spot 21 of the laser beam 20 has a crescent shape or a stepped energy distribution. Its highest energy point is precisely aligned with the edge of the pre-stressed layer L3 as described above, using stress to guide the crack, while the lowest energy point is aligned with the middle area in the width direction of the cutting zone, avoiding excessive ablation of the central area and achieving the aforementioned good effect. In terms of the process flow, the pretreatment operation and the main cutting step can be integrated into one process flow, ensuring synergistic effects through precise alignment.

[0095] In some embodiments, when performing stealth cutting, the highest energy value of the laser beam used on the structure to be processed SS containing the stress layer L3 can be lower than the highest energy value of the laser beam used on the structure to be processed SS without the stress layer L3. This is because the silicon material has been "pre-treated", the presence of the stress layer reduces the cutting difficulty, and the energy of the main cutting laser can be lower, fundamentally reducing the energy source of sputtering damage.

[0096] This approach helps reduce the energy of the laser beam used during cutting. In this embodiment, crack propagation is dominated by the stress field, rather than simply the thermal field, resulting in higher precision and virtually zero splash damage. It also helps guide the crack to propagate along the stress layer, preventing incorrect cutting positions and further improving cutting yield.

[0097] In this embodiment, the formation of the stress layer L3 and the laser beam obtained after the initial laser beam shaping operation need to cooperate and work together to achieve a good cutting effect. In some embodiments, the energy value of the preset region Qc with the lowest energy is 0. In some embodiments, such as Figure 16 and Figure 17 As shown, the laser beam 20 includes a first laser beam 201 and a second laser beam 202. The first laser beam 201 has a preset spot 21. The maximum energy of the second laser beam 202 is less than 1 / 20 of the maximum energy of the first laser beam 201. The second laser beam 202 is emitted within a preset time after the first laser beam 201 is emitted.

[0098] In some embodiments, the ratio of the maximum energy of the second laser beam 202 to the maximum energy of the first laser beam 201 is 0.01, 0.02, 0.03, 0.04, etc.

[0099] In some embodiments, the laser beam 20 may also contain a greater number of laser beams, which can be set according to actual needs and is not specifically limited here.

[0100] In this embodiment, a single laser beam is split into two or more laser beams, and a time dimension is introduced. The two or more laser beams are emitted sequentially during operation. The first laser beam emitted at the beginning is the main laser beam, which uses a preset "strong first, weak later" beam pattern (with energy distribution adjusted by beam skewness spatial filtering) and is responsible for completing the main material modification (e.g., silicon modification) and crack propagation. One or more laser beams following the main laser beam are auxiliary laser beams, which emit a suppression pulse with extremely low energy and a larger beam pattern within a very short time (e.g., picoseconds) after the main laser beam. This pulse does not produce modification; its function is to rapidly heat and "smooth" the molten silicon formed by the main pulse, or to suppress the escape of sputtered particles through photopressure.

[0101] This process can be referenced. Figure 16 and Figure 17 Understanding the diagram, after the first laser beam 201 completes irradiation, an initial modified layer 11a is formed, and spatter P caused by the irradiation of the first laser beam 201 may exist around it. After irradiation by the second laser beam 202, the edges of the initial modified layer 11a can change from a sharp state to a smooth state to enhance the modification effect and obtain the desired modified layer 11. At this time, the spatter P can become less prone to migration under the action of the second laser beam 202, and may even form a stable substance E fixed within the preset cutting area, preventing migration and sputtering damage during subsequent main laser beam irradiation.

[0102] In some embodiments, when the laser beam comprises multiple laser beams, the next laser beam begins to emit within a picosecond time after the previous laser beam is emitted.

[0103] In embodiments where the laser beam is divided into two or more laser beams, the first laser beam can be any of the laser beams provided in the foregoing embodiments. Besides achieving the aforementioned effects, this also helps improve the morphology of the modified layer, making it more uniform and reducing the randomness of microcracks. In this embodiment, further suppression of sputtering damage can be achieved, potentially controlling the sputtering distance to a smaller range, such as <5µm.

[0104] In some embodiments, after forming a modified layer 11 inside the structure to be treated SS using a laser beam 20, the preparation method further includes: applying an external force to the structure to be treated SS, causing cracks 12 to extend along the modified layer 11 to the surface of the cutting area Qb to divide the structure to be treated SS.

[0105] In some embodiments, the purpose of segmenting the structure SS can be achieved by adhering a blue film to the surface of the structure SS to be processed.

[0106] This disclosure also provides a laser cutting apparatus 100, such as... Figure 19 As shown, the laser cutting apparatus 100 for cutting semiconductor structures includes: Laser A1 is used to generate the initial laser beam 20a; The beam shaping unit A2 is configured to perform shaping operations on the initial laser beam 20a to obtain a laser beam 20 with a preset spot 21. The focusing unit A3 is used to guide the laser beam 20 to the middle region of the cutting area Qb of the structure to be treated SS along the thickness direction, and to form a modified layer 11 and a crack 12 extending from the modified layer 11 along the thickness direction of the structure to be treated SS inside the structure to be treated. Motion unit A4 moves one of the laser beam 20 and the structure to be processed SS along the preset cutting trajectory D0 to adjust the relative position between the laser beam 20 and the structure to be processed SS. The preset light spot 21 has a first axis of symmetry Oa perpendicular to the preset cutting trajectory D0, and the energy distribution of the preset light spot 21 on both sides of the first axis of symmetry Oa is asymmetrical.

[0107] In some embodiments, the initial laser beam 20a is a Gaussian beam.

[0108] In some embodiments, laser A1 is at least one of lasers that emits near-infrared laser, far-infrared laser, or other infrared bands, green laser, or ultraviolet laser, and the emitted laser pulse width is nanosecond, picosecond, or femtosecond.

[0109] In some embodiments, laser A1 is at least one of lasers capable of emitting near-infrared or far-infrared wavelengths.

[0110] In some embodiments, the beam shaping unit A2 includes, but is not limited to, a laser beam modulator (LBA) or a structure consisting of multiple lenses.

[0111] In some embodiments, such as Figure 3 As shown, the beam shaping unit A2 can shape the initial laser beam 20a emitted by the laser to obtain a laser beam 20 with an asymmetric energy distribution on both sides of the first axis of symmetry Oa, which can have the following characteristics: Figures 4 to 7 The preset laser spot 21 shown, when used with the shaped laser beam 20 to perform a cutting operation (stealth cutting) on ​​the structure SS to be processed, can achieve a cutting effect that significantly reduces sputtering damage and makes the sputtering range significantly controllable. This is beneficial for improving the cutting yield and ultimately the electrical performance and reliability of the semiconductor structure. For more details on the effects, please refer to the relevant descriptions in the preparation method examples, which will not be repeated here.

[0112] In some embodiments, the beam shaping unit A2 is configured to perform a shaping operation on the initial laser beam 20a to obtain a laser beam 20 with a preset spot 21, including: By importing different computer-generated holograms (CGH images) into the laser beam modulator, the energy distribution of the incident Gaussian beam can be altered, resulting in an asymmetrical energy distribution of the beam spot. Assuming that the pixel coordinates of the energy center point in the initial laser beam 20a are (0, 0), the energy density at the center point is the highest. After performing a shaping operation on the initial laser beam 20a, the pixel coordinates of the energy center can be shifted, for example, to (1, 0), which is a shift in the horizontal coordinate, i.e., the point with the highest energy density moves horizontally.

[0113] In some embodiments, the apparatus further includes an optical path unit A5 configured to transmit an initial laser beam 20a to a beam shaping unit A2.

[0114] In some embodiments, such as Figures 3 to 7 As shown, along a first direction parallel to the direction of movement of the laser beam 20 on the structure SS to be processed, the preset spot 21 includes multiple regions with energy densities distributed from high to low.

[0115] For details regarding the settings and effects of the laser beam corresponding to the preset spot 21 provided in any embodiment, please refer to the aforementioned preparation method embodiments; further details will not be provided here.

[0116] In some embodiments, the preset light spots 21 corresponding to two laser beams 20 emitted sequentially at any adjacent time are respectively defined as the first preset light spot 211 and the second preset light spot 212. The region with the lowest energy in the first preset light spot 211 is located at the edge of the first preset light spot 211, and the lowest energy value in the first preset light spot 211 is denoted as A. Among them, the orthographic projection of the first preset spot 211 on the structure to be processed SS and the orthographic projection of the second preset spot 212 on the structure to be processed SS have an overlapping area Qd. Along a first direction parallel to the movement direction of the laser beam 20 on the structure to be processed SS, the overlapping area Qd is located in the middle region. The overlapping area Qd is composed of the orthographic projection of the region with energy value A in the first preset spot 21 on the structure to be processed SS and the orthographic projection of the region with energy value not less than A in the second preset spot 21 on the structure to be processed SS.

[0117] For information on the overlapping region Qd between two adjacent laser beams 20, please refer to the preparation method section; it will not be elaborated here.

[0118] In some embodiments, when a stress layer L3 needs to be set in the structure to be processed SS, the laser cutting device 100 further includes a pre-processing unit, which can add a pre-processing module (such as a UV laser or plasma source) to an existing stealth cutting (SD) device, and use a low-energy, large-spot ultraviolet laser or plasma to perform non-destructive surface treatment at the position corresponding to the cutting area Qb on the back of the silicon wafer to form an extremely thin (nanoscale) compressive stress layer.

[0119] In some embodiments, when the laser beam 20 includes two or more laser beams, and the two or more laser beams are emitted sequentially in the time dimension, the number of lasers in the laser cutting device 100 can be multiple. For example, a dual (or multiple) laser system or a single laser beam splitting and passing through a delay line can generate time-controllable main / auxiliary laser beam pulses. The main laser beam pulse corresponds to a laser beam whose energy is asymmetrically distributed about the first axis of symmetry Oa, and the auxiliary laser beam corresponds to a laser beam with energy much lower than that of the main laser beam.

[0120] In some embodiments, the desired two or more laser beams can be obtained by generating a corresponding CGH image for each laser beam. In some embodiments, the auxiliary laser beam can be a flat-top beam or an anti-Gaussian distributed beam.

[0121] The technical features described in the embodiments provided in this disclosure can be arbitrarily combined without conflict.

[0122] The above are merely preferred embodiments of this disclosure and are not intended to limit the scope of protection of this disclosure. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure.

Claims

1. A method for fabricating a semiconductor structure, characterized in that, include: A structure to be processed is provided, the structure to be processed including a cutting area and a functional area located between adjacent cutting areas; An initial laser beam is generated, and the initial laser beam is shaped to obtain a laser beam with a preset spot, and the laser beam is guided to the middle region of the cutting area along the thickness direction; The laser beam and the structure to be processed are moved along a preset cutting trajectory to adjust the relative position between the laser beam and the structure to be processed. The laser beam is used to form a modified layer and cracks extending from the modified layer along the thickness direction of the structure to be processed inside the structure to be processed. The preset light spot has a first axis of symmetry perpendicular to the preset cutting trajectory, and the energy distribution of the preset light spot on both sides of the first axis of symmetry is asymmetrical.

2. The preparation method according to claim 1, characterized in that, Along a first direction parallel to the direction of movement of the laser beam on the structure to be processed, the preset spot includes multiple regions with energy densities distributed from high to low.

3. The preparation method according to claim 2, characterized in that, The number of regions is N, and the N regions are respectively denoted as the first region, the second region, ..., the Nth region, where N is a positive integer greater than or equal to 2. The second region, ..., the Nth region are sequentially nested around the outer periphery of the first region along a direction away from the geometric center of the first region. The geometric center of the Nth region coincides with the geometric center of the preset light spot, and the geometric centers of the first region, the second region, ..., the Nth region are offset in a second direction opposite to the first direction relative to the geometric center of the Nth region in a first direction.

4. The preparation method according to claim 3, characterized in that, Along the first direction, the preset light spot has a first end and a second end that are arranged opposite to each other, and the distance between the geometric center of the first region and the first end is less than the distance between the first region and the second end; The distance between the geometric center of the first region, the second region, ..., the Nth region and the first end increases sequentially.

5. The preparation method according to claim 4, characterized in that, Along the first direction, the distance between the geometric center points of adjacent regions is the same.

6. The preparation method according to claim 4, characterized in that, The laser beam forms a modified layer inside the structure to be treated, comprising: The energy from the first region to the Mth region in the preset light spot forms a modified layer inside the structure to be processed, where M is a positive integer and 1≤M<N.

7. The preparation method according to claim 1, characterized in that, A structure to be processed is provided, the structure including cutting areas and functional areas located between adjacent cutting areas; including: A wafer is provided, the wafer including a substrate and a device layer located on the substrate, the dicing region dividing the substrate and the device layer into a plurality of functional regions; Moving one of the laser beam and the structure to be processed along the preset cutting trajectory to adjust the relative position between the laser beam and the structure to be processed, and using the laser beam to form a modified layer inside the structure to be processed, including: The laser beam is moved along the preset cutting trajectory to adjust the relative position between the laser beam and the wafer. The laser beam irradiates the structure to be processed from the side of the substrate away from the device layer to form a modified layer inside the substrate and cracks extending from the modified layer along the thickness direction of the structure to be processed.

8. The preparation method according to claim 1, characterized in that, A structure to be processed is provided, the structure including cutting areas and functional areas located between adjacent cutting areas; including: The system provides at least two wafers stacked vertically, with the exposed surfaces of the two outermost wafers defined as a first surface and a second surface, respectively, and a bonding layer disposed between adjacent wafers; the dicing region divides the stacked wafers into multiple functional areas. Moving one of the laser beam and the structure to be processed along the preset cutting trajectory to adjust the relative position between the laser beam and the structure to be processed, and using the laser beam to form a modified layer and cracks extending from the modified layer along the thickness direction of the structure to be processed inside the structure to be processed, including: The laser beam is moved along a preset cutting trajectory to adjust the relative position between the laser beam and the at least two wafers. The laser beam irradiates the structure to be processed from the side where the first surface is located to form a first modified layer inside the bonding layer and a first crack extending from the first modified layer along the thickness direction of the structure to be processed. The laser beam is moved along the preset cutting trajectory to adjust the relative position between the laser beam and the at least two wafers. The laser beam irradiates the structure to be processed from the side where the second surface is located to form a second modified layer inside the bonding layer and a second crack extending from the second modified layer along the thickness direction of the structure to be processed. The first modified layer and the second modified layer constitute the modified layer, and the first crack and the second crack constitute the crack.

9. The preparation method according to any one of claims 1, 7, or 8, characterized in that, Extending along a direction perpendicular to the cutting area, the cutting area includes an intermediate region that provides the structure to be processed, including: A stress layer is formed on a predetermined surface in the thickness direction of the structure to be processed, extending into the interior of the structure to be processed, and the stress layer is located in the cutting area; In a direction parallel to the surface of the structure to be processed and perpendicular to the preset cutting trajectory, the preset light spot includes multiple preset regions with energy distributed from high to low. Guiding the laser beam to the middle region of the cutting area along the thickness direction includes: The preset region with the highest energy in the preset light spot is aligned with the edge of the stress layer away from the middle region, and the preset region with the lowest energy in the preset light spot is aligned with the middle region.

10. The preparation method according to claim 9, characterized in that, The energy value of the preset region with the lowest energy is 0.

11. The preparation method according to any one of claims 1-8 or 10, characterized in that, The laser beam includes a first laser beam and a second laser beam. The first laser beam has the preset spot. The maximum energy of the second laser beam is less than 1 / 20 of the maximum energy of the first laser beam. The second laser beam is emitted within a preset time after the first laser beam is emitted.

12. The preparation method according to any one of claims 1-8 and 10, characterized in that, During the process of moving the laser beam along a preset cutting trajectory to one of the structures to be processed in order to adjust the relative position between the laser beam and the structure to be processed, the preset light spots corresponding to the two laser beams emitted in any adjacent time are respectively defined as the first preset light spot and the second preset light spot. The region with the lowest energy in the first preset light spot is located at the edge of the first preset light spot, and the lowest energy value in the first preset light spot is denoted as A. Wherein, the orthographic projection of the first preset light spot on the structure to be processed and the orthographic projection of the second preset light spot on the structure to be processed have an overlapping area. Along a first direction parallel to the moving direction of the laser beam on the structure to be processed, the overlapping area is located in the middle region. The overlapping area is formed by the overlapping part of the orthographic projection of the region with energy value A in the first preset light spot on the structure to be processed and the orthographic projection of the region with energy value not less than A in the second preset light spot on the structure to be processed.

13. The preparation method according to claim 12, characterized in that, After forming a modified layer inside the structure to be treated using the laser beam, the preparation method further includes: applying an external force to the structure to be treated, causing the crack to extend along the modified layer to the surface of the cutting area to divide the structure to be treated.

14. A laser cutting device, characterized in that, The apparatus for cutting semiconductor structures includes: A laser, used to generate an initial laser beam; A beam shaping unit is configured to perform shaping operations on the initial laser beam to obtain a laser beam with a preset spot. A focusing unit is used to guide the laser beam to the middle region along the thickness direction of the cutting area of ​​the structure to be treated, and to form a modified layer and a crack extending from the modified layer along the thickness direction of the structure to be treated inside the structure to be treated. The motion unit moves one of the laser beam and the structure to be processed along a preset cutting trajectory to adjust the relative position between the laser beam and the structure to be processed. The preset light spot has a first axis of symmetry perpendicular to the preset cutting trajectory, and the energy distribution of the preset light spot on both sides of the first axis of symmetry is asymmetrical.

15. The apparatus according to claim 14, characterized in that, The device also includes an optical path unit configured to transmit the initial laser beam to the beam shaping unit.

16. The apparatus according to claim 14, characterized in that, The beam shaping unit includes, but is not limited to, a laser beam adjuster or a structure consisting of multiple lenses.

17. The apparatus according to any one of claims 14-16, characterized in that, Along a first direction parallel to the direction of movement of the laser beam on the structure to be processed, the preset spot includes multiple regions with energy densities distributed from high to low.

18. The apparatus according to claim 17, characterized in that, The preset light spots corresponding to two laser beams emitted sequentially at any adjacent time are respectively defined as the first preset light spot and the second preset light spot. The region with the lowest energy in the first preset light spot is located at the edge of the first preset light spot, and the lowest energy value in the first preset light spot is denoted as A. Wherein, the orthographic projection of the first preset light spot on the structure to be processed and the orthographic projection of the second preset light spot on the structure to be processed have an overlapping area. Along a first direction parallel to the moving direction of the laser beam on the structure to be processed, the overlapping area is located in the middle region. The overlapping area is formed by the overlapping part of the orthographic projection of the region with energy value A in the first preset light spot on the structure to be processed and the orthographic projection of the region with energy value not less than A in the second preset light spot on the structure to be processed.

Images